If you don't have a characteristic coastline, you can easily do "Yamadate" with a compass glass.
Use compass glasses with high waterproof performance.

1. First, set one point (palm tree) on the coastline and read the compass direction.
   <Figure 1>

2. Next, set another point (hotel) on the coastline and read the compass direction.
   <Figure 2>

3. The water surface position is determined.

Try to intersect the two straight lines as vertically as possible in order to know the exact water surface position.